Radial contact switch



May 29, 1951 J. A. SCHWARZ 2,554,506

RADIAL CONTACT SWITCH Filed May 2l, 1947 2 SheeTfS-Sheet l ZZ /U /47 Y. 0 O

A\ o f,

l Q z5 Patented May 29, 1951 RADIAL CONTACT SWITCH Joseph A. Schwarz, Chicago, Ill., assigner to Birtman Electric Com Illinois pany, a corporation of Application May 21, 1947, Serial No. 749,553

v's claims. (o1. 20o- 8) This invention relates to a motor control for an electric motor.

The invention, which is the subject of this application, is drawn to'that type of motor control wherein the speed of the motor is regulated by having tapped leads or electrical conduits leading to the eld coils of the motor and a contact member movable from one contact Ato the other. This type of control is simple and inexpensive, but has not always been satisfactory in the past due to the inefliciency of the control means used to energize the various f1eld circuits. Also, many ofthese controls in the past have been too large and bulky to be used on small motors. The control means of this invention overcomes these difficulties as it is quite small yet is eilicient in operation. I t may be used on small motors such as those employedfin food mixers and is inexpensive to build and efficient in operation.

v The invention will be described as related to one embodiment of the same as shown in the accompanying drawings. Of the drawings: Fig. 1 is an elevation oa portable motor adapted for use on food mixers and the like with portions in section for clarity of illustration; Fig. 2 is a plan view of the motor of Fig. l; Fig. 3 is an enlarged sectional view of the motor control used on the motor shown in Figs. 1 and 2*; Fig. 4 is a section taken along line 4 4 of Fig. 3; Fig. 5 is a View similar to Fig. 3 but showing the movable portion of the motor'control in an intermediate position between the contacts; Fig. 6 is a section taken along line 6 5 of Fig. 5;

and Fig. 7 is a diagrammatic view showing one l embodiment of the electrical circuit to the motor. Although the motor control will be described herein as applied to a food mixer motor, it is believed obvious that it can be used for other types of motors. Y

The motor shown in the accompanying drawings comprises a casing I9 having top`lllaand bottom Ib air portsior the circulation of cooling air, a handle II, a housing I2 for the drive shaft, a beater shaft I3 attached to theI drive shaft, and a motor control I4 mounted on the top portion of the handle I I. Y

The motor controln I4 comprises a housing I5 divided into two symmetrical parts and provided with a central cavity Ia therein. These two parts are held together by three spaced rivets I5 located around the periphery vof the housing. The bottom portion of the housing I5 is provided with three spaced openings I5b -extending into the central cavity Ia andin'which are located contact members I'I. These openings 15b are formed of cooperating grooves in each part of the housing I5'so that when the parts are arranged together, the openings will be defined. Each contact member II has an enlarged head portion I'Ia provided with a depressed portion I'Ib in its inner end adjacent the cavity I5a. This cavity has an approximately semicircular bottom wall.

Rotatably mounted within the cavity I5@ there is located an approximately circular rotatable member I8 that is rotatably-mounted on a rivet I9 held in the housing. This rotatable member has a major portion of its outer edge provided with serrations Id with the unserrated portion Y IBb extending beyond the serrations and arrivet ranged adjacent'the-contact members l1.y Located within the rotatable member I8 is a cylin drical opening [8c extending from the surface of the unserrated portion Iilb tothe mounting I9. Located within the opening Ilc is a detent 2l) having a rounded-head 29a adapted to engage alternately the depressed portion I'Ib of the contact membersll. This detent 2lliis urged outwardly by a compression spring 2I extending between the detentand'the mounting rivet- I9. This spring serves to hold the detent in engagement with a'contact member I'I. The detent 20 is provided with anA inwardly extending circular portion 2m) locatedV substantially concentric to the spring 2l so as to aid in properly locating the spring. I

The housing I5 is adapted to be fastened to a curved plate 22 having an opening therein through which the rotatable member IB extends. This curved plate may be'fastened to the outside surface of the top part of the handle II, as shown in Figs. l and 2, with the housing extending into ahole Y23 in this top portion of the handle. This provides a smooth surface with the rotatable member I8 extending beyond the surface and in a position to be operated by the thumb of a hand grasping the `handle I I, as shown in Fig. l. Y rEach of the contact members I'I is electrically connected to theel-d coil of the motor by means of an insulated wire 24. The electrical circuit through the control members is provided by arranging a plate 25 on the side of the housing I5 with this plate extending between 'the lowest housing rivet I6 and the mounting rivet I@ for the rotatable member IIS;` A wire 26 is attached to the plate 25 as by soldering. This'wire is intended to be connected to a source of electric Current when the motor is being operated. With this arrangement, the electrical circuit is completed through the plate 25, the mounting rivet I9, the spring 2I, a contact member l'I, and a wire 24 to the field of the motor.

The surface of the central cavity 55a in the housing I5 opposite the edge of the rotatable member I8 is provided with three spaced raised portions I5c with one raised portion being between the first and second contact member, a second raised portion between the second and third contact member, and a third raised portion"Y beyond the third contact member. These raised portions are provided with longitudinal grooves I5d so that when the rotatable member 'I8- is turned the detent 26 will ride on the edges of these grooves as shown in Fig. 6. This reduces the frictional drag on the detent. The last raised portion I5c aids in positioning the detent in an off position. When the detent is moved over this last raised portion, it is held so that it will not be accidentally moved to a'contact member. 'This arrangement is shown in Fig. 5. As was explained above, the housing I5 is divided into two similar cooperating portions. The plane that divides the housing passes through the rotatable member I8, the spring 2I, the detent 20, the raised portions I5c, the grooves |511, and the contact members I'I. This arrangement aids in'assemblingthe motor control. l

The wiring diagram for a typical motor using the motor control lof this invention is shown diagrammatically in Fig. 7. As is here shown, one Wire 26 from the source of electricity is led to the'motor control. A low speed contact I'Ic is led through a wire 24a to a tap 2l on a field coil 28.` Another contact member I'I'd is led through a wire 2lb to one side of the eld coil 28 and to a tap 29 on another field coil 39. The third contact member I'Ie is led through a wire 24e to one side of a eld coil 3B. Another Wire 3I that'is adapted to be connected to a source of electricity is attached to'a third field coil 3'2 and the eld coil 28 at the end which is opposite thewire 24h connected to the armature 33. The other side of the armature is connected to the eld coil 32 on the end opposite the Wire 3i. In a typical installation, 'eld coil 28 will consist of 425 turns of No. 27 wire with the tap 2l being located at 175 turns from the end of the coil opposite the armature, field coil 3Q may consist of 250 turns of No. 27 wire, while coil'f32 may consist of 150 turns of No. 26 wire. This will provide an approximately 11a-"horsepower motor operating at 490 R. P. M. onrcontact member llc, approximately G50 R. P.- M.' on contact member l'ld, and approximately 1200 R. P. M. on contact member Ille. The 01T position, as shown in Fig. 5, may be located opposite either contact member I'Ic or IIe.A "It is preferred, however, that it be located opposite the low speed contact IIc. As can be lseen in Fig. '7, when the motor control is moved from'a low to a high speed position more of the field coils will be energized. It is, of course, obvious that other arrangements may be used on diiTerent types of motors With the control means of this invention being used on almost any type of motor. Having described my invention as related to the embodiment shown in the accompanying drawings, it is my intention that the invention be not limited by any of the details of description unless otherwise specified but ratherA be construed broadly within its spirit and scope 'as set out in the accompanying claims. j Y

-I claim: Y Y 1. An electrical control apparatus comprising a rotatable member, a plurality of spaced electrical contacts arranged adjacent the rotatable member, a contact member mounted on the rotatable member and adapted to engage said contacts successively as the rotatable member is turned, and a groove between each pair of adjacent contacts with the contact member adapted to engage only the edges of said groove to reduce the frictional drag on said contact member when said member is moved from one contact to another.

2. An electrical control apparatus comprising a rotatable member, a housing around at least a portion of said member, an electrically conducting axle in said housing upon which said rotatable member is mounted, a plurality of electrical contacts in said housing arranged adjacent'the edge of said rotatable member, an electrical contact member held by said rotatable member at the edge thereof to engage the contacts alternately, and spring means bearing against said axle and said Contact member to urge the contact member outwardly in engagement with said contacts, said axle, spring means" and contact member forming an electrical cir`A cuit.

3. The apparatus of claim 2 wherein said axle extends to the outer surface of said housing, and' there is provided an electrically conducting plate member xedly mounted on the outer surface of said housing with said axle engaging said plate member, said electrical circuit including saidl plate member.

fl. An electrical control apparatus comprising a rotatable member, a housing around at least a portion of said member, a plurality7 of spaced electrical contacts in said housing arranged adjacent the edge of said rotatable member, a raised portion between each adjacent pair of contacts with each raised portion having 'a groove in the surface thereof adjacent the rol tatable member, each groove having substan-l tially parallel edges, an electrical contact mem-l ber held by said rotatable member at the edge4 thereof to engage said contacts alternately and' having a rounded outer end, said rounded outer end of the contact member having a, Widthgreater than that or" said groove so thatthe member bears against only said outer edges of the groove in a raised portion to reduce the frictional drag' on said contact member when moving from one Contact member to the next.

5. An electrical control apparatus comprising a rotatable member, an electrical conducting axlevon which said rotatable member is mounted, a housing therearound from which the edge porfv tion ofr the rotatable member extends to provide a hand-engageable portion, a plurality of elec-A trical contacts in said housing arranged'adjacent the inner edge of said rotatable member, araised portion between each adjacent pair` of contacts and extending toward the edge of said rotatable member, an electrical contact member held by said rotatable member and rotatable therewith to engage the contacts alternately, said contact member passing over said raised portions when being moved along the contacts, and spring means urging the contact member outwardly, said spring means being electrically attached to said axle and to said contactmernber vand the electrical circuit in the control apparatus including said axle and spring means.' 6. An electrical control apparatus comprising a rotatable member, a housing therearound from which the edge portion of the rotatable memberA extends to provide a hand-engageable portion, a plurality of electrical contacts in said housing arranged adjacent the inner edge of said rotatable member, a raised portion between each adjacent pair of contacts and extending toward the -edge of said rotatable member, an electrical contact member held by said rotatable member and rotatable therewith to engage the contacts alternately, said contact member passing over said raised portions When being moved along the contacts, and spring means urging the contact member outwardly, said raised portion being provided With a longitudinal groove With the contact member engaging the edges of said groove during the travel of the contact member.

JOSEPH A. SCHWARZ.

REFERENCES CITED The following references are of record in the le of this patent:

6 UNITED STATES PATENTS Number Number 

